Problem: Apply the distributive property to factor out the greatest common factor. $40f+30 =$
$ {10}$ is the greatest common factor of $40f$ and $30$. $\phantom{=}40f+30$ $={10}\cdot 4f+{10}\cdot3$ $={10}(4f+3)~~~~~~~~$ Apply the distributive property. The answer: $ {10}(4f+3) $